Dynamic Reference Frames for California
Abstract
Maintenance of a fixed geodetic datum in California is complicated by a variety of motions at different spatial and temporal scales. The motions are the result of tectonic and magmatic processes and vertical land motion due to natural (e.g., drought) and/or anthropogenic effects (e.g., water and mineral extraction). To address this difficulty the California Spatial Reference Center (CSRC) has published five "Epoch Date" reference frames since 2002, as a realization of a California Spatial Reference System (CSRS). The latest is "CSRS Epoch 2017.50 (NAD83)," defined by the geodetic coordinates and uncertainties of the 948 California Spatial Reference Network (CSRN) continuous GNSS stations (839 active and 109 defunct) on July 2, 2017). It is aligned with the current definition of the National Spatial Reference System (NSRS) through a set of coordinate transformations from ITRF2014 to NAD83(2011), published by the NOAA/NOS National Geodetic Survey (NGS). The NGS will replace NAD83 by the North American Terrestrial Reference Frame of 2022 (NATRF 2022) closely anchored to the North American plate. However, the extreme western portions of the continental U.S. are not on the North American plate and experience significant motions that need to be considered as a supplement to the 2022 update. The NOAA Technical Report NOS NGS 62, 2017 "Blueprint for 2022, Part 1: Geometric Coordinates" acknowledges the need for a supplemental Intra-Frame Velocity Model (IFVM) for the "Intra-Plate zones" but leaves undefined how this might be developed, funded or implemented. We present a study funded by the California Department of Transportation that considers a dynamic reference frame for California that could replace the Epoch Date approach and allow a seamless and continuous tie to NATRF 2022. The reference frame is based on the gridded residuals between an underlying fault slip model for the Western U.S. by Zeng and Shen (JGR Solid Earth, 2017) and daily displacements of the continuous GNSS CSRN stations estimated by the Scripps Orbit and Permanent Array Center (SOPAC) from 2010 to the end of 2017. Vertical geodetic motions are estimated directly from the daily displacements without an underlying vertical model and can be supplemented with a geoid model such as GEOID12B published by the NGS to maintain a regional vertical reference frame.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.G41A..04B
- Keywords:
-
- 1204 Control surveys;
- GEODESY AND GRAVITYDE: 1214 Geopotential theory and determination;
- GEODESY AND GRAVITYDE: 1217 Time variable gravity;
- GEODESY AND GRAVITYDE: 1229 Reference systems;
- GEODESY AND GRAVITY